[entropy.server.db] use revision from package data if none is forced

this avoids the generation of packages with lesser revisions during
package moves from a repo to another.
If we inherit the revision number, we should try to keep it as long
as there are no packages with greater revision number in the target
repository.

lib/entropy/server/interfaces/db.py

@@ -252,8 +252,11 @@ class ServerPackagesRepository(CachedRepository):
             pkg_data['category'], pkg_data['name'], pkg_data['version'],
             pkg_data['versiontag'])
 
+        increase_revision = False
         if revision is None:
-            current_rev = -1
+            current_rev = max(
+                pkg_data.get('revision', 0),
+                0)
         else:
             current_rev = revision
 
@@ -263,14 +266,16 @@ class ServerPackagesRepository(CachedRepository):
 
             if revision is None:
                 pkg_revision = self.retrieveRevision(package_id)
-                current_rev = max(pkg_revision, current_rev)
+                if pkg_revision >= current_rev:
+                    current_rev = pkg_revision
+                    increase_revision = True
 
             manual_deps |= self.retrieveManualDependencies(package_id,
                 resolve_conditional_deps = False)
             # injected packages wouldn't be removed by addPackage
             self.removePackage(package_id)
 
-        if revision is None:
+        if increase_revision:
             current_rev += 1
 
         # manual dependencies handling